Magnetic screw driver



Feb. 26, 1957 DE ALT E. WILLIAMS, JR 2,732,323

MAGNETIC SCREW DRIVER Filed April 12, 1954 lllllllllll M lmlL 41 u L I. r I

INVENTOR.

Da AL T E.W|LLIAMS,JR. BY

ATTORNEYS United States MAGNETIC SCREW DRIVER De Alt E. Williams, Jr., Dayton, Ohio, assignor to The Apex Machine and Tool Company, Dayton, Ohio, a corporation of Ohio Application April 12, 1954, Serial No. 422,462

1 Claim. (Cl. 145-51) This invention relates to magnetic screw drivers, and more particularly to a composite magnetic screw driver assembly incorporating a bit holder and a separate bit.

a It is a primary object of the present invention to provide a magnetic screw driver assembly wherein the bit holder part of the assembly carries a permanent magnet capable of magnetizing a bit held thereby and wherein the bit in turn carries a finder sleeve mounted for lengthwise movement thereon and constructed to cooperate with the bit in aligning the bit with the screw to be driven without interfering with the desired magnetic attraction of the bit for the screw.

A further object of the invention is to provide a magnetic screw driver assembly wherein the bit and the finder sleeve thereon carry a spring which cooperates therewith to bias the bit to a normal position wherein its rearward end projects from the sleeve for insertion in a magnetic bit holder and wherein its forward working end is retained just within the forward end of the sleeve for positive magnetic engagement with the screw to be driven thereby in order to assure maintained magnetic attraction of the bit for the screw.

It is also an object of the invention to provide a magnetic screw driver assembly as outlined above wherein the finder sleeve is formed of non-magnetic material in order to direct the magnetic flux from the magent toward the working end of the bit to assure maintained magnetic attraction of the bit for the screw driven thereby, and further to provide such a magnetic screw driver assembly in which the bit holder also includes a non-magnetic socket portion similarly operating to direct the magnetic flux as desired toward the working end of the bit.

Additional objects and advantages of the invention will be apparent from the following description, the accom panying drawing and the appended claim.

In the drawing- Fig. 1 is a side elevational view of a magnetic screw driver assembly constructed in accordance with the invention;

Fig. 2 is an enlarged view taken partly in section on the line 22 of Fig. 1;

Fig. 3 is a further enlarged fragmentary section showing the bit and finder sleeve in operative relation with a screw; and

Fig. 4 is a view similar to Fig. 3 showing the operation of the assembly to hold the screw after the latter has been unscrewed from the work.

Referring to the drawing, which illustrates a preferred embodiment of the invention, the bit holder comprises a generally cylindrical part which is preferably of non magnetic material such as beryllium copper alloy hardened by suitable heat treatment after forming to the desired shape. The rearward end of the holder part 10 is broached at 11 to receive the press-fitted hexagonal portion 12 of the shank 13, the rearward end of which is shaped as desired to be received in a suitable chuck or driver. Silver solder 14 or the like is applied around the section, for receiving a complementarily shaped bit. An

internal peripheral groove 16 near the forward end of socket 15 receives a split retaining ring 17 for the bit, the ring extending into this groove and having its inner surface projecting radially inwardly of the socket to engage the bit. Between the socket 15 and the broached portion 11, the bit holder 10 is provided with a smaller cylindrical bore containing an elongated bore-type permanent magnet 20.

The bit 22 is shown as having a hexagonal rear end for driven fit within the socket 15, and the forward end of the bit has a working end 25 shown as of the chisel type for engagement in a conventional slotted-head screw. The rearward end of the bit is provided at its corners with a series of small notches 26 in position to be engaged by the ring 17 when the bit is mounted Within the socket 15. The bit can be inserted and withdrawn from operative position in the bit holder by applying suflicient axial pressure to cause the retainer ring 17 to be lifted out of the notches 26, the ring however being resilient to develop suflicient force for holding the bit in place during normal working operations. The bit 22 should be formed of magnetic material such as steel so that when it is mounted in the socket 15 as shown in Fig. 2, it will be in effective magnetic contact with the magnet 20 for magnetizing thereby.

The bit 22 carries a finder sleeve 30 of non-magnetic material such as beryllium copper alloy in order to direct the magnetic fiux from the magnet 20 to the point 25 when the bit is in working position. The rearward end of the sleeve 30 has an enlarged bore terminating in an annular shoulder 31 which forms a seat for a coil spring 33. The rearward end of this spring seats on a split ring 34 mounted in a suitable peripheral groove on the bit. The sleeve and bit are retained in this assembled relation by means of a split ring 35 received within the retaining groove 36 near the rearward end of the sleeve, and a slot 37 in the end of the sleeve provides access to this ring for release thereof.

At its forward end, the finder sleeve 30 is provided with an enlarged bore terminating in an annular shoulder 40 forming a seat limiting insertion into the sleeve of the head of the screw to be driven, as illustrated by the screw 41 in Fig. 4. In order, however, to assure maintained magnetic attraction of the bit for the screw, the parts are so proportioned that in the normal rearward position of the bit with respect to the finder sleeve as established by the retainer ring 35, the point 25 of the bit projects slightly beyond the radial plane of the seat 40 as shown in Figs. 2 and 4. Satisfactory results have been obtained in operation with a total such projection by the point 25 of the order of 0.015 inch.

Figs. 3 and 4 illustrate the operation of this screw driver assembly to unscrew .a screw 41 from work pieces 44 and 45. The assembly is simply set down in such *manner that the forward end of the sleeve 30 fits over the screw head 41 and bottoms on the Work piece 44. Then when thrust is applied on the bit holder, the bit 22 will advance against spring 33 until it touches the screw head, and it is then rotated until it indexes within the slot in the screw head. The unscrewing of the screw is then carried out in the usual way until it is entirely released from the work, during which operation the screw head will move back into the sleeve to the extent permitted by the shoulder 40. At the same time, the bit will also retract within the finder sleeve, but it will be stopped as described while retained in magnetic engagement with the screw so that when the latter is fully rea a ea-s2 t I leased, it will still be held magnetically and thus withdrawn completely from the work and finally manually detached from the bit.

It will accordingly be seen that the screw driver asseiribly of the invention incorporates the important advantages of a magnetic screw driver as well as those of a findersleeve and a removable and replaceable bit. The effective operation of the magnetic parts of the assembly is assured as described by the construction of the finder sleeve and bit holding socket of non-magnetic material, and it is also desirable to construct both the spring 33 and the retainer ring 35 of non-magnetic material such as the same beryllium copper alloy noted above. In this manher, the magnetic flux is definitely directed from the magnet toward and into the working end of the bit to assure maintained magnetic attraction of the bit for the screw, and with the parts proportioned as disclosed, the screw is held in the desired strong magnetic engagement with the bit even after being withdrawn from the work.

While the form of apparatus herein described constitutes a preferred embodiment of the invention, it is to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claim.

What is claimed is:

A magnetic screw driver assembly comprising a bit holder including means defining a socket of non-circular section, a bit of magnetic material having the forward working end thereof formed to drive a screw and having the rearward end thereof complementary in section to said socket for driven fit therein, a sleeve shorter than said bit mounted on said bit for movement lengthwise therereceived over the head of a screw to be driven by said of, the forward end of said sleeve being formed to be bit and having an annular seat therein limiting reception of said screw head therein, a spring mounted within said sleeve in cooperative relation with said bit and biasing said bit rearwardly to a normal position wherein said working end thereof is retracted within said forward end of said sleeve while said rearward end of said bit projects beyond said sleeve for engagement within said bit holder socket, a permanent bar magnet within said socket in position to magnetlze said bit upon insertion thereof in said socket, said sleeve and said socket being of non-magnetic material to direct the magnetic flux toward said working end of said bit causing said bit to retain said head of said screw within said forward end of said sleeve by magnetic attraction, cooperating stop means on said bit and said sleeve limiting retractive movement of said bit in said sleeve to a normal position of said working end thereof spaced between the forward end of said sleeve and the radial plane of said seat in said sleeve to assure maintained magnetic attraction of said bit and said screw, and means limiting insertion of said bit in said socket to cause said bit to be projected forwardly of said sleeve into firm driving engagement with said screw in response to a thrust force applied to said bit holder relative to said sleeve.

References Cited in the file of this patent UNITED STATES PATENTS 1,769,067 Meunier July 1, 1930 2,260,055 Reardon Oct. 21, 1941 2,276,470 Dodelin Mar. 17, 1942 2,475,936 Allen July 12, 1949 2,522,217 Fischer et a1 Sept. 12, 1950 2,550,775 Clark May 1, 1951 

